Typically, a seat belt pretensioner is activated by an electrical signal which travels over a conductive wire. The pretensioner is hard-wired to a suitable power source for providing power to the pretensioner. The pretensioner usually includes an electrically actuated squib which initiates flow of inflation fluid to tighten a seat belt around a vehicle occupant. Because it is desirable to actuate the pretensioner only when the occupant is belted in the seat, a sensor is used to detect when a belted condition exists. Typically, an additional electrical conductor provides power from the power source to the buckle sensor.